Parametric amplifiers

ABSTRACT

In a parametric amplifier wherein a diode is disposed in a pumping waveguide at the junction between a pumping waveguide and a coaxial line including central conductor connected to the diode, a recess for receiving the diode is formed in the pumping waveguide with a portion of the periphery of the recess disposed to intersect one wall defining the hollow passage of the waveguide. As nearly all portions of the periphery of the diode are surrounded by the metal of the waveguide, the reactance exhibited by a portion of the pumping waveguide can be decreased.

United States Patent [56] References Cited FOREIGN PATENTS 715,199 8/1965 Canada 330/49 964,982 7/1964 Great Britain 330/49 Primary Examiner- Roy Lake Assistant Examiner-Darwin R. Hostetter Attorneys-Robert E. Burns and Emmanuel .l. Lobato ABSTRACT: In a parametric amplifier wherein a diode is disposed in a pumping waveguide at the junction between a pumping waveguide and a coaxial line including central conductor connected to the diode, a recess for receiving the diode is formed in the pumping waveguide with a portion of the periphery of the recess disposed to intersect one wall defining the hollow passage of the waveguide. As nearly all portions of the periphery of the diode are surrounded by the metal of the waveguide, the reactance exhibited by a portion of the pumping waveguide can be decreased.

[72] Inventor Takeo Fukuda Kawasakl-shi, Japan [21] Appl. No. 877,228

[22] Filed Nov. 17, 1969 [45] Patented Nov. 30, 1971 [73 Assignee Tokyo Shlbaura Denki Kabushlki Kaisha (a/k/a Tokyo Shlbatira Electric Co., Ltd.) Kawasaki-shi, Kanagawa-ken, Japan [32] Priority Nov. 29, 1968 [33] Japan [54] PARAMETRIC AMPLIFIERS 5 Claims, 5 Drawing Figs.

[52] U.S. Cl. 330/49, 3 30/34 [51 Int. Cl 1103! 7/04 [50] Field of Search 330/49, 34

PATENTED NUV30 l97| PRlOR ART PRIOR ART F I 4 PARAMETRIC AMPLIFIERS BACKGROUND OF THE INVENTION This invention relates to a parametric amplifier wherein the reactance exhibited by a portion of the pumping waveguide is minimized.

In a diode parametric amplifier, it is necessary to couple the diode with a signal circuit, an idler circuit and a pumping circuit. In a prior arrangement, in view of the easiness of the coupling between the diode and pumping circuit and simplicity of construction, the diode is disposed in the hollow passage of the waveguide. However, as will be discussed later in more detail, this arrangement results in increases Qs of the signal and idler resonance circuits, the degrading the characteristics of the amplifier. To solve this problem, it has been proposed to reduce the height of the pumping waveguide and hence the reactance thereof. Although this solution is efiective for relatively low-signal frequencies of the order of less than several GHz., the effect of the reactance becomes substantial for much higher frequencies, thus greatly degrading the characteristics of the parametric amplifier.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide an improved parametric amplifier wherein the reactance exhibited by a portion of the pumping waveguide is greatly reduced for signal frequencies of millimeter wave range or submillimeter waves.

According to this invention, in a parametric amplifier wherein a diode is disposed in a pumping waveguide at the junction between the waveguide and a coaxial line including a central conductor connected to the diode, there is provided a recess in the pumping waveguide to receive the diode in a manner such that a portion of the periphery of the recess intersects one side or end wall of the walls which define the hollow passage of the waveguide. With this construction, since nearly all portions of the periphery of the diode are surrounded by the metal of the waveguide, the reactance exhibited by a portion of the pumping waveguide can be greatly decreased, and yet sufficient coupling is provided between the diode and the pumping waveguide through that portion of the periphery of the recess which intersects the side or end wall of the hollow passage of the waveguide.

BRIEF DESCRIPTION OF THE DRAWING The invention can be better understood from the following detailed description taken in conjunction with the accompanying drawing in which:

FIG. 1 shows an arrangement of a diode of a prior art parametric amplifier;

FIG. 2 shows a cross section of the parametric amplifier taken along a line IIII in FIG. 1;

FIG. 3 is an equivalent circuit of the parametric amplifier shown in FIGS. 1 and 2;

FIG. 4 is a sectional view of a parametric amplifier embodying the present invention taken along a line IV-IV in FIG. 5 and FIG. 5 is a sectional view of the parametric amplifier taken along a line V-V in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT As has been pointed out hereinabove, in a prior art parametric amplifier, a diode is secured at the center of a hollow passage 12 of a pumping waveguide 11 at the junction thereof with a coaxial line 13 consisting of an outer conductor 14 having a central passage 15 and a central conductor 16 contained in the central passage 15 and connected to one terminal of diode I0. The cross-sectional configuration of the coaxial line 13 may be circular, square or rectangular. The coaxial line may be connected to the pumping waveguide by any suitable means such as screws and the like. With this prior arrangement, however, as the diode 10 is disposed in the hollow passage 12 the reactance X exhibited by the pumping waveguide and included in series with the diode is high as diagrammatically shown by the equivalent circuit shown in FIG. 3, in which elements bounded by dot and dash lines represent the diodes 10. As a consequence, the Qs of the signal and idler resonance circuits are increased, thus degrading the characteristics of the amplifier. The prior art approach for solving this problem by decreasing by height of the pumping waveguide is effective only for signal frequencies of less than several GHz. but not for higher frequencies.

According to this invention, as shown in FIGS. 4 and 5, a circular recess 17 is formed in the waveguide 11 at a position coaxial with the central passage 15 of the coaxial line 13 with a portion 19 of the periphery of circular recess 17 disposed to intersect one sidewall 18 defining the hollow passage 12 of waveguide 11. The axis of the coaxial line 13 is offset from the longitudinal axis of hollow passage 12. As before, the crosssectional area of the coaxial line 13 may be circular, square or rectangular. With any cross-sectional configuration, the line 13 is comprised by a central conductor 16 and a hollow conductor l4 surrounding the same. With this construction, substantially all of the periphery of the recess 17 except the small opening 19 is surrounded by the metal of pumping waveguide 11 so that the reactance exhibited by a portion of the pumping waveguide is greatly decreased in comparison with that of the prior construction wherein the diode is not surrounded by metal.

In an actual parametric amplifier wherein the width a of the hollow passage 12 was 3.5 mm., the height b thereof was 0.8 mm., the diameter 0 of the central passage 15 was 2.0 mm., and the type M8559 diode (manufactured by Tokyo Shibaura Electric Co., Cj=0.25 pH, Ls=0.l3 nh.) was used, the series resonance frequency of the circuit of FIG. 3 including diode and reactance X was 15 Gl-lz. with the prior art construction shown in FIGS. 1 and 2, whereas with the construction of the invention shown in FIGS. 4 and 5, the series resonance frequency was increased to 22 GI-Iz.

Further, notwithstanding the position of the diode 10, which is not located at the center of the hollow passage 12 but at one sidewall thereof, the coupling between diode l0 and the pumping waveguide was not decreased, because the opening 19 provides sufficient coupling. Instead of locating the recess 17 to intersect one sidewall 18 of the hollow passage, it may be located to intersect one end wall of the hollow passage 12. Further, instead of connecting the coaxial line to the pumping waveguide so that the axis of the coaxial line is perpendicular to the axis of the diode, if desired, the coaxial line may be connected to the waveguide so that the axis of the coaxial line intersects at right angles the axis of the diode.

I claim:

1. In a parametric amplifier wherein a diode is disposed at the junction between a pumping waveguide having a hollow passage and a coaxial line including a central conductor connected to said diode, the improvement which comprises a recess provided in said pumping waveguide to receive said diode, a portion of the periphery of said recess intersecting a portion of a wall defining said hollow passage whereby substantially all of the periphery'of said diode is surrounded by g the metal of said pumping waveguide so as to decrease the reactance exhibited by a portion of the pumping waveguide.

2. The parametric amplifier according to claim 1 wherein the axis of said coaxial line is ofiset from the longitudinal axis of said hollow passage, and said recess is coaxial with the axis of said coaxial line.

3. In a parametric amplifier, the combination of a pumping waveguide having a hollow passage of rectangular cross section with opposite broad walls connected by opposite narrow walls, a coaxial line disposed approximately perpendicular to said broad walls of said hollow passage and offset laterally of said hollow passage, said coaxial line comprising an outer conductor, a central passage offset laterally of but intersecting a said narrow wall of said hollow passage to provide a junction of said passages, and a central conductor in said central passage, and a diode disposed in said central passage at said passage of said coaxial line. junction and having a terminal connected to said central con- 5 A parametric lifi cording to daim 3 in which ducmr' coaxial line terminates in a cavity communicating with said 4. A parametric amplifier according to claim 3, in which said diode is offset laterally outside the Plane of said narrow 5 hello, passage sald diode being disposed m said cavity sidewall of said hollow passage intersected by said central 

1. In a parametric amplifier wherein a diode is disposed at the junction between a pumping waveguide having a hollow passage and a coaxial line including a central conductor connected to said diode, the improvement which comprises a recess provided in said pumping waveguide to recEive said diode, a portion of the periphery of said recess intersecting a portion of a wall defining said hollow passage whereby substantially all of the periphery of said diode is surrounded by the metal of said pumping waveguide so as to decrease the reactance exhibited by a portion of the pumping waveguide.
 2. The parametric amplifier according to claim 1 wherein the axis of said coaxial line is offset from the longitudinal axis of said hollow passage, and said recess is coaxial with the axis of said coaxial line.
 3. In a parametric amplifier, the combination of a pumping waveguide having a hollow passage of rectangular cross section with opposite broad walls connected by opposite narrow walls, a coaxial line disposed approximately perpendicular to said broad walls of said hollow passage and offset laterally of said hollow passage, said coaxial line comprising an outer conductor, a central passage offset laterally of but intersecting a said narrow wall of said hollow passage to provide a junction of said passages, and a central conductor in said central passage, and a diode disposed in said central passage at said junction and having a terminal connected to said central conductor.
 4. A parametric amplifier according to claim 3, in which said diode is offset laterally outside the plane of said narrow sidewall of said hollow passage intersected by said central passage of said coaxial line.
 5. A parametric amplifier according to claim 3, in which coaxial line terminates in a cavity communicating with said hollow passage, said diode being disposed in said cavity. 